A Grammatical Dictionary of Botanical Latin

Calathidium,-ii (s.n.II), abl. sg. calathidio; calathium,-ii (s.n.II), abl. sg. calathio: the capitulum of Compositae; "the head of a Composite; preferably restricted to the involucre of the same" (Jackson) [> dim. of Gk. calathos (s.m.II), also L. calathus,-i (s.m.II)]; apparently a synonym of synanthium, q.v., a capitulum, as in Compositae: synanthium,-ii (s.n.II), abl.sg. synanthio;

Flowers (‘flosculi’ of many authors) hermaphroditic or by abortion unisexual, [many] more rarely single on a common receptacle (‘clinanthium’ of many authors), sessile or subsessile, with a common involucre (‘periclinium’ of many authors) enclosed [by, or from] bracts (‘scales’, ‘phylla’ [‘leaves’, used for ‘bracts’] or ‘phyllaries’ of many authors), one to (indeterminately) seriate, free or compound [grown together], forming a capitulum (‘anthodium’ or ‘calathidium’ of many authors) simulating a single flower.